1. Field of the Invention
The present invention relates generally to coating glass and, more specifically, to an apparatus and method for applying a protective coating to a glass pane using a screen printing process.
2. Description of the Related Art
An automotive windshield is generally shatter-proof and typically manufactured by using two pieces of glass pane with a clear film laminated therebetween. When a force sufficient to break the glass panes is imparted to the windshield, the clear film holds broken glass in place as part of the whole windshield and prevents the glass panes from shattering, thereby protecting the passengers or others from the deleterious effects of flying sharp pieces of broken glass.
Typically, the windshield is bonded to the vehicle about the peripheral edges of the glass panes using an adhesive well known in the art for such purposes. However, certain disadvantages exist when the adhesive is continuously or repeatedly exposed to ultraviolet light from the sun. Ultraviolet light may cause the adhesive to degrade, losing its bonding characteristics and possibly causing the windshield to separate from the vehicle.
In order to overcome these disadvantages, it is known in the art to coat the glass panes with an ultraviolet protective coating or paste which may resemble paint or ink at the periphery of the glass panes and corresponding to the area where the adhesive is applied. This is done using conventional screen printing processes. More specifically, a glass pane is supported in an apparatus including a print screen disposed in spaced relationship over the glass and the screen is covered with an ultraviolet protective coating. The print screen is deflected into contact with the glass pane typically by squeegees. The squeegees move the protective coating across the print screen and into contact with the glass pane to deposit the protective coating in predetermined points on the glass pane. Examples of apparatuses and methods for applying a coating using screen printing processes are disclosed in U.S. Pat. No. 5,050,498 issued to Smith on Sep. 24, 1991 for a Stencil Manufacturing Process And Apparatus and U.S. Pat. No. 5,273,780 issued to Borger et al. on Dec. 28, 1993 for Screen Printing A Glass Pane With A Decorative Coating Including Blowing Away Or Sucking Printing Ink From The Edge Of The Glass Pane.
Generally, automotive windshields are manufactured in factories which can become hot due to the heat generated in the glass manufacturing process as well as the ambient temperature of the air, especially in the Summer months. In the past, when oil based ultraviolet protective coatings were typically employed, there has been a problem with evaporation of the ultraviolet protective coating due to this heat. This problem is further compounded with the move to water based ultraviolet protective coatings. High ambient temperatures can decrease curing time of the ultraviolet protective coating. Both conditions may degrade the protective feature of the ultraviolet protective coating and are undesirable.
Lowering the temperature at the ultraviolet protective coating stage of the manufacturing process through air conditioning or building a separate climate controlled area or booth have been deemed too costly. Still, the need to retard the evaporation of the ultraviolet protective coating and lengthen the curing time of the same remains.